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Journal logoCRYSTALLOGRAPHIC
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ISSN: 2056-9890
Volume 71| Part 7| July 2015| Pages o449-o450

Crystal structure of (1R,4R)-tert-butyl 3-oxo-2-oxa-5-aza­bi­cyclo­[2.2.2]octane-5-carboxyl­ate

aDepartment of Applied Chemistry, Kyushu Institute of Technology, Kitakyushu 804-8550, Japan, and bGraduate School of Life Sciences and Systems Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550, Japan
*Correspondence e-mail: suvrathak@gmail.com

Edited by G. Smith, Queensland University of Technology, Australia (Received 1 May 2015; accepted 1 June 2015; online 6 June 2015)

In the title compound, C11H17NO4, commonly known as N-tert-but­oxy­carbonyl-5-hy­droxy-D-pipecolic acid lactone, the absolute configuration is (1R,4R) due to the enantiomeric purity of the starting material which remains unchanged during the course of the reaction. In the crystal there no inter­molecular hydrogen bonds.

1. Related literature

For background information on 5-hy­droxy­pipecolic acid and related compounds, see: Witkop & Foltz (1957[Witkop, B. & Foltz, C. M. (1957). J. Am. Chem. Soc. 79, 192-197.]); Hoarau et al. (1996[Hoarau, S., Fauchère, J. L., Pappalardo, L., Roumestant, M. L. & Viallefont, P. (1996). Tetrahedron Asymmetry, 7, 2585-2593.]); Sun et al. (2008[Sun, C. S., Lin, Y. S. & Hou, D. R. (2008). J. Org. Chem. 73, 6877-6880.]). For the synthesis of a related compound, see: Krishnamurthy et al. (2014[Krishnamurthy, S., Arai, T., Nakanishi, K. & Nishino, N. (2014). RSC Adv. 4, 2482-2490.]). For crystal structures of related lactones, see: (1S,4S) conformer, racemic mixture, Moriguchi, Krishnamurthy, Arai & Tsuge (2014[Moriguchi, T., Krishnamurthy, S., Arai, T. & Tsuge, A. (2014). J. Crystallogr.: doi 10.1155/2014/150796.]); Moriguchi, Krishnamurthy, Arai, Matsumoto et al. (2014[Moriguchi, T., Krishnamurthy, S., Arai, T., Matsumoto, T., Araki, K., Tsuge, A. & Nishino, N. (2014). J. Crystallogr.: doi 10.1155/2014/645079]).

[Scheme 1]

2. Experimental

2.1. Crystal data

  • C11H17NO4

  • Mr = 227.26

  • Orthorhombic, P 21 21 21

  • a = 9.6472 (4) Å

  • b = 9.7084 (4) Å

  • c = 12.2323 (5) Å

  • V = 1145.66 (8) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.10 mm−1

  • T = 90 K

  • 0.45 × 0.40 × 0.40 mm

2.2. Data collection

  • Bruker APEX2 KY CCD diffractometer

  • Absorption correction: multi-scan SADABS (Bruker, 2009[Bruker (2009). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.870, Tmax = 0.961

  • 13518 measured reflections

  • 2791 independent reflections

  • 2728 reflections with I > 2σ(I)

  • Rint = 0.021

2.3. Refinement

  • R[F2 > 2σ(F2)] = 0.030

  • wR(F2) = 0.081

  • S = 1.03

  • 2791 reflections

  • 148 parameters

  • H-atom parameters constrained

  • Δρmax = 0.24 e Å−3

  • Δρmin = −0.27 e Å−3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), 2933 Friedel pairs

  • Absolute structure parameter: 0.1 (7)

Data collection: APEX2 (Bruker,2009[Bruker (2009). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2009[Bruker (2009). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); software used to prepare material for publication: SHELXL97.

Supporting information


Comment top

5-Hydroxypipecolic acid is a higher homologue of 4-hydroxyproline, which is found in dates (Witkop & Foltz, 1957). 4-Hydroxyproline is formed by post-translational modification of proline in collagen and is responsible for enhancing its stability. Literature reports the synthesis of 5-hydroxypipecolic acid derivatives (Hoarau et al., 1996; Sun et al., 2008), generally forming diastereomeric mixtures of cis- and trans-5-hydroxypipecolic acids. Therefore such syntheses suffer from disadvantages of separation of the diasteromers making the procedure very tedious. A facile procedure to isolate this amino acid was desirable.

Our previous communication reported the synthesis of a 4-hydroxyproline derivative from an amino acid bearing epoxide (Krishnamurthy et al. 2014). It is reported in this study that the cis-isomer undergoes intramolecular lactonization to tert-butyl- 3-oxo-2-oxa-5-azabicyclo[2.2.1]heptane-5-carboxylate, making the isolation from the trans ester highly feasible. Based on this observation it can be expected that cis-5-hydroxypipecolic acids would also undergo in situ intramolecular lactonization. In fact, when a mixture of a cis- and trans-5-hydroxypipecolic acid derivatives was reacted under acidic conditions, the cis-isomer successfully converted to the lactone (I), subsequently readily separated from the remaining trans--isomer. We had previously reported the crystal structure of racemic tert-butyl- 3-oxo-2-oxa-5-azabicyclo[2.2.2]octane-5-carboxylate (Moriguchi, Krishnamurthy, Arai, Tsuge et al., 2014) and (1S,4S)-tert-butyl 3-oxo-2-oxa-5-azabicyclo[2.2.2]octane-5-carboxylate (Moriguchi, Krishnamurthy, Arai, & Tsuge, 2014). Herein we would like to report the crystal structure of enantiomerically pure (1R,4R)-tert-butyl- 3-oxo-2-oxa-5-azabicyclo[2.2.2]octane-5-carboxylate, C11H17N O4, (I).

The title compound (I), commonly known as N-tert- butoxycarbonyl-5-hydroxy-D-pipecolic acid lactone, was derived from a starting product having a cis configuration for both hydroxyl and carboxyl groups, leading to lactone formation (Fig. 1). The nitrogen atom N1 appears next to the bridge-head atom within the bicyclic ring system. The absolute configuration of the compound was found to be (1R,4R) due to the configuration of the starting material (Fig. 3). The Flack structure parameter (Flack, 1983) determined for (I) [0.1 (7)], although not definitive because of the uncertainty factor, is considered to provide adequate supporting evidence for this configuration. The desired hydrophobic conformer (1R,4R), (I) was easily isolated from hydrophylic (1R,4S)–(4) (Fig. 3). The intramolecular lactonization is possible only in (1R,4R)–(3) isomer due to its configuration. The hydroxyl and the carboxyl groups are in close proximity due to the cis- configuration of (1R,4R)–(3), which leads to the intamolecular lactonization with loss of EtOH. With the (1R,4S)–(4) isomer the hydroxyl and the carboxyl groups are far apart due to the trans- configuration, thus preventing the lactonization. In the crystal there no formal intramolecular hydrogen bonds (Fig. 2).

This work represents the first structural characterization of this (1R,4R)- aza and oxa bicyclic chiral lactone characterized by X-ray analysis.

Related literature top

For background information on 5-hydroxypipecolic acid and related compounds, see: Witkop & Foltz (1957); Hoarau et al. (1996); Sun et al. (2008). For the synthesis of a related compound, see: Krishnamurthy et al. (2014). For crystal structures of related lactones, including the (1S,4S) conformer, see: Moriguchi, Krishnamurthy, Arai & Tsuge (2014); Moriguchi, Krishnamurthy, Arai, Matsumoto et al. (2014).

Experimental top

The basic reaction scheme for preparation of the title compound (I) is shown in Fig. 3. To a ice cooled solution of 4 mol/L HCl in 1,4-dioxane (16 mL), a solution of diastereomeric (1) ( 0.97 g, 3.56 mmol) in 0.5 mL of 1,4-dioxane was added. This reaction mixture was then warmed to room temperature and stirred. After 3 h most of the volatile materials were removed under vacuum resulting in a crude oily mixture. Trituration with diethyl ether followed by decantation resulted in (2) as a foam (0.71 g, 95 %). DIEA (0.89 mL, 5.07 mmol) was added to a solution of (2) ( 0.71 g, 3.38 mmol) in DMF (13 mL) and stirred at 50 °C. After 6 h the solution was warmed to room temperature, followed by addition of Boc2O (3.96 g, 18.1 mmol), additional DIEA (0.3 mL, 1.69 mmol) and stirred at room temperature for 18 h. The DMF was evaporated and the crude mixture was subsequently washed with 10% aqueous citric acid, 4% aqueous NaHCO3, brine, dried (MgSO4), filtered and evaporated to obtain an oil. The crude product was purified by silica gel column chromatography with (CHCl3/MeOH, 100:0 to 98:2, v/v) to yield (1R,4R), (I) (0.18 g, 23%) as a white solid. Single crystals were obtained by vapour diffusion method at room temperature, i.e., hexane vapour was allowed to diffuse into an EtOAc (0.5 ml) solution of (1R,4R), (I) at room temperature. Single crystals suitable for analysis were obtained after a week.

1H NMR 4.61-4.82 (2H, m), 3.63 (1H, m), 3.45 (1H, m), 2.22 (1H, br s), 2.11 (1H, m), 2.00 (1H, m), 1.80 (1H, m), 1.47 (9H, s); MS (FAB m/z): 228 (74), 190 (44), 172 (100), 137 (50), 128 (68), 55 (47). HRMS(FAB) calcd for C11H18N1O4 [M + H]+ 228.12358, found 228.1243

Refinement top

All hydrogen atoms were placed in calculated positions (C—H = 0.98–1.00 Å) and allowed to ride, with UisoH = 1.5UeqC(methyl) or 1.2UeqC(methine and methylene). The absolute structure parameter (Flack, 1983) for (I) [0.01 (7) for 2933 Friedel pairs], although not definitive is sufficient to confirm the (1R,4R) identity, as distinct from that of the known (1S,4S) conformer (Moriguchi, Krishnamurthy, Arai & Tsuge, 2014).

Computing details top

Data collection: APEX2 (Bruker,2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. Molecular configuration and atom numbering scheme for the title compound with displacement ellipsoids drawn at the 50% probability level. Hydrogen atoms are omitted for clarity.
[Figure 2] Fig. 2. Crystal packing diagram of the title compound.
[Figure 3] Fig. 3. Synthetic scheme for the title compound (I).
(1R,4R)-tert-butyl 3-oxo-2-oxa-5-azabicyclo[2.2.2]octane-5-carboxylate top
Crystal data top
C11H17NO4Dx = 1.318 Mg m3
Mr = 227.26Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P212121Cell parameters from 9630 reflections
a = 9.6472 (4) Åθ = 2.7–28.7°
b = 9.7084 (4) ŵ = 0.10 mm1
c = 12.2323 (5) ÅT = 90 K
V = 1145.66 (8) Å3Prism, colorless
Z = 40.45 × 0.40 × 0.40 mm
F(000) = 488
Data collection top
Bruker APEX2 KY CCD
diffractometer
2791 independent reflections
Radiation source: fine-focus sealed tube2728 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.021
Detector resolution: 16.6666 pixels mm-1θmax = 28.7°, θmin = 2.7°
ϕ and ω–scansh = 1212
Absorption correction: multi-scan
SADABS (Bruker, 2009)
k = 1212
Tmin = 0.870, Tmax = 0.961l = 1616
13518 measured reflections
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.030 w = 1/[σ2(Fo2) + (0.0583P)2 + 0.1302P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.081(Δ/σ)max < 0.001
S = 1.02Δρmax = 0.24 e Å3
2791 reflectionsΔρmin = 0.27 e Å3
148 parametersExtinction correction: SHELXL97
0 restraintsExtinction coefficient: 0.0015
Primary atom site location: structure-invariant direct methodsAbsolute structure: Flack (1983), 2933 Friedel pairs
Secondary atom site location: difference Fourier mapAbsolute structure parameter: 0.1 (7)
Crystal data top
C11H17NO4V = 1145.66 (8) Å3
Mr = 227.26Z = 4
Orthorhombic, P212121Mo Kα radiation
a = 9.6472 (4) ŵ = 0.10 mm1
b = 9.7084 (4) ÅT = 90 K
c = 12.2323 (5) Å0.45 × 0.40 × 0.40 mm
Data collection top
Bruker APEX2 KY CCD
diffractometer
2791 independent reflections
Absorption correction: multi-scan
SADABS (Bruker, 2009)
2728 reflections with I > 2σ(I)
Tmin = 0.870, Tmax = 0.961Rint = 0.021
13518 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.030H-atom parameters constrained
wR(F2) = 0.081Δρmax = 0.24 e Å3
S = 1.02Δρmin = 0.27 e Å3
2791 reflectionsAbsolute structure: Flack (1983), 2933 Friedel pairs
148 parametersAbsolute structure parameter: 0.1 (7)
0 restraints
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C10.65404 (10)0.31574 (9)0.06026 (7)0.01427 (18)
H10.710.29370.00630.017*
C20.49996 (10)0.33409 (10)0.03171 (8)0.0176 (2)
H2A0.46280.24850.00110.021*
H2B0.48830.410.02150.021*
C30.42204 (10)0.36786 (11)0.13907 (9)0.0206 (2)
H3B0.3780.45970.13350.025*
H3A0.34850.29870.15210.025*
C40.52501 (11)0.36654 (10)0.23335 (8)0.01785 (19)
H40.4750.38360.30370.021*
C50.63878 (10)0.47291 (11)0.21909 (8)0.0178 (2)
H5B0.59930.5670.21750.021*
H5A0.70640.46710.27980.021*
C60.66134 (10)0.19956 (10)0.14366 (8)0.01762 (19)
C70.81399 (10)0.51222 (9)0.07261 (8)0.01444 (19)
C80.96933 (10)0.70326 (10)0.12123 (8)0.01618 (19)
C91.10001 (11)0.61760 (12)0.11084 (11)0.0276 (2)
H9A1.09640.56380.04310.041*
H9B1.10720.55510.17350.041*
H9C1.1810.67850.10920.041*
C100.94288 (14)0.79172 (11)0.02135 (10)0.0272 (3)
H10A0.86220.85070.03450.041*
H10B0.9250.73240.04190.041*
H10C1.02430.84920.00690.041*
C110.97332 (14)0.79157 (13)0.22359 (10)0.0311 (3)
H11A0.98660.73250.28770.047*
H11B0.88580.8420.23070.047*
H11C1.05020.85720.21840.047*
N10.70560 (9)0.44009 (8)0.11448 (7)0.01612 (17)
O10.71703 (8)0.08995 (8)0.13238 (7)0.02526 (18)
O20.59161 (8)0.23044 (8)0.23684 (6)0.01975 (16)
O30.86922 (8)0.48744 (7)0.01469 (6)0.01893 (16)
O40.84801 (7)0.61426 (7)0.14236 (6)0.01846 (16)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0141 (4)0.0119 (4)0.0168 (4)0.0019 (3)0.0008 (3)0.0028 (3)
C20.0155 (5)0.0172 (4)0.0201 (4)0.0010 (4)0.0030 (3)0.0007 (3)
C30.0129 (4)0.0230 (5)0.0259 (5)0.0005 (4)0.0000 (4)0.0014 (4)
C40.0160 (4)0.0179 (4)0.0196 (4)0.0001 (4)0.0032 (4)0.0012 (4)
C50.0166 (4)0.0198 (4)0.0172 (4)0.0019 (4)0.0050 (3)0.0052 (3)
C60.0143 (4)0.0171 (4)0.0215 (5)0.0016 (3)0.0017 (4)0.0002 (4)
C70.0145 (4)0.0126 (4)0.0162 (4)0.0002 (3)0.0017 (3)0.0000 (3)
C80.0151 (4)0.0155 (4)0.0179 (4)0.0058 (4)0.0001 (3)0.0001 (3)
C90.0166 (5)0.0241 (5)0.0421 (6)0.0010 (4)0.0024 (4)0.0012 (5)
C100.0361 (6)0.0179 (5)0.0275 (5)0.0039 (4)0.0051 (4)0.0051 (4)
C110.0330 (6)0.0349 (6)0.0255 (6)0.0171 (5)0.0039 (5)0.0126 (5)
N10.0161 (4)0.0161 (4)0.0162 (4)0.0040 (3)0.0032 (3)0.0056 (3)
O10.0252 (4)0.0171 (3)0.0334 (4)0.0050 (3)0.0025 (4)0.0002 (3)
O20.0211 (4)0.0186 (3)0.0195 (3)0.0009 (3)0.0015 (3)0.0029 (3)
O30.0219 (4)0.0184 (3)0.0165 (3)0.0038 (3)0.0041 (3)0.0022 (3)
O40.0175 (3)0.0185 (3)0.0194 (3)0.0073 (3)0.0040 (3)0.0059 (3)
Geometric parameters (Å, º) top
C1—N11.4645 (11)C6—O21.3570 (12)
C1—C61.5225 (13)C7—O31.2175 (12)
C1—C21.5373 (14)C7—O41.3481 (11)
C1—H11.0C7—N11.3587 (12)
C2—C31.5482 (14)C8—O41.4776 (11)
C2—H2A0.99C8—C91.5156 (15)
C2—H2B0.99C8—C101.5150 (14)
C3—C41.5222 (15)C8—C111.5180 (14)
C3—H3B0.99C9—H9A0.98
C3—H3A0.99C9—H9B0.98
C4—O21.4699 (13)C9—H9C0.98
C4—C51.5171 (13)C10—H10A0.98
C4—H41.0C10—H10B0.98
C5—N11.4677 (12)C10—H10C0.98
C5—H5B0.99C11—H11A0.98
C5—H5A0.99C11—H11B0.98
C6—O11.2000 (12)C11—H11C0.98
N1—C1—C6106.95 (7)O3—C7—O4126.43 (9)
N1—C1—C2109.62 (8)O3—C7—N1124.45 (9)
C6—C1—C2106.43 (8)O4—C7—N1109.12 (8)
N1—C1—H1111.2O4—C8—C9110.65 (8)
C6—C1—H1111.2O4—C8—C10109.82 (8)
C2—C1—H1111.2C9—C8—C10112.55 (9)
C1—C2—C3107.54 (8)O4—C8—C11101.89 (8)
C1—C2—H2A110.2C9—C8—C11110.98 (10)
C3—C2—H2A110.2C10—C8—C11110.44 (9)
C1—C2—H2B110.2C8—C9—H9A109.5
C3—C2—H2B110.2C8—C9—H9B109.5
H2A—C2—H2B108.5H9A—C9—H9B109.5
C4—C3—C2108.91 (8)C8—C9—H9C109.5
C4—C3—H3B109.9H9A—C9—H9C109.5
C2—C3—H3B109.9H9B—C9—H9C109.5
C4—C3—H3A109.9C8—C10—H10A109.5
C2—C3—H3A109.9C8—C10—H10B109.5
H3B—C3—H3A108.3H10A—C10—H10B109.5
O2—C4—C5107.40 (8)C8—C10—H10C109.5
O2—C4—C3108.35 (8)H10A—C10—H10C109.5
C5—C4—C3112.29 (9)H10B—C10—H10C109.5
O2—C4—H4109.6C8—C11—H11A109.5
C5—C4—H4109.6C8—C11—H11B109.5
C3—C4—H4109.6H11A—C11—H11B109.5
N1—C5—C4105.68 (8)C8—C11—H11C109.5
N1—C5—H5B110.6H11A—C11—H11C109.5
C4—C5—H5B110.6H11B—C11—H11C109.5
N1—C5—H5A110.6C7—N1—C1121.03 (8)
C4—C5—H5A110.6C7—N1—C5123.69 (8)
H5B—C5—H5A108.7C1—N1—C5115.13 (8)
O1—C6—O2120.96 (9)C6—O2—C4113.01 (7)
O1—C6—C1126.91 (9)C7—O4—C8120.79 (7)
O2—C6—C1112.10 (8)
N1—C1—C2—C356.55 (10)C6—C1—N1—C7123.18 (10)
C6—C1—C2—C358.77 (10)C2—C1—N1—C7121.84 (9)
C1—C2—C3—C41.58 (11)C6—C1—N1—C552.53 (11)
C2—C3—C4—O257.69 (10)C2—C1—N1—C562.46 (10)
C2—C3—C4—C560.76 (11)C4—C5—N1—C7179.64 (9)
O2—C4—C5—N161.20 (10)C4—C5—N1—C14.06 (11)
C3—C4—C5—N157.81 (10)O1—C6—O2—C4177.27 (9)
N1—C1—C6—O1126.60 (11)C1—C6—O2—C40.91 (11)
C2—C1—C6—O1116.29 (11)C5—C4—O2—C661.30 (10)
N1—C1—C6—O255.36 (10)C3—C4—O2—C660.21 (10)
C2—C1—C6—O261.75 (10)O3—C7—O4—C84.98 (15)
O3—C7—N1—C15.74 (15)N1—C7—O4—C8175.60 (8)
O4—C7—N1—C1174.83 (8)C10—C8—O4—C767.57 (11)
O3—C7—N1—C5178.93 (9)C9—C8—O4—C757.30 (12)
O4—C7—N1—C50.50 (13)C11—C8—O4—C7175.35 (9)

Experimental details

Crystal data
Chemical formulaC11H17NO4
Mr227.26
Crystal system, space groupOrthorhombic, P212121
Temperature (K)90
a, b, c (Å)9.6472 (4), 9.7084 (4), 12.2323 (5)
V3)1145.66 (8)
Z4
Radiation typeMo Kα
µ (mm1)0.10
Crystal size (mm)0.45 × 0.40 × 0.40
Data collection
DiffractometerBruker APEX2 KY CCD
diffractometer
Absorption correctionMulti-scan
SADABS (Bruker, 2009)
Tmin, Tmax0.870, 0.961
No. of measured, independent and
observed [I > 2σ(I)] reflections
13518, 2791, 2728
Rint0.021
(sin θ/λ)max1)0.676
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.030, 0.081, 1.02
No. of reflections2791
No. of parameters148
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.24, 0.27
Absolute structureFlack (1983), 2933 Friedel pairs
Absolute structure parameter0.1 (7)

Computer programs: APEX2 (Bruker,2009), SAINT (Bruker, 2009), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

 

Acknowledgements

We are grateful to the Center for Instrumental Analysis, Kyushu Institute of Technology (KITCIA), for high-resolution mass and 1H NMR spectra and X-ray analysis.

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Volume 71| Part 7| July 2015| Pages o449-o450
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